Inexcusable.
The "benefit" for Rocco and Neri was that, by humiliating Tom publicly, he made it impossible for either of them to disagree with whacking Roth. So, when he turned and said, "Rocco?" poor Rocco had no choice but to say, "Difficult, not impossible" if he didn't want to be put in the same sh*t-can that Michael had just put Tom. It was Michael at his most ruthlessly manipulative.
Exactly, and he was also playing Rocco so he would think that if he volunteered to go on the Roth suicide mission and somehow survive, he would become Neri's equal.
